In fuel injection valves for engines, it is important to atomize the fuel injection spray sufficiently from viewpoints of toxic substance reduction in emission gas, fuel consumption performance improvement and so on. U.S. Pat. Nos. 6,405,946-B1, 6,616,072-B2, US-2004-0124279-A1 and their counterpart JP-2001-46919-A disclose fluid injection nozzles for promoting an atomization of the fuel injection spray.
In the fluid injection nozzles disclosed in the above publications, a flat disc-shaped fuel chamber is formed between a valve seat and injection ports. By the fuel chamber provided between the valve seat and the injection ports, fuel, which has flown on an inner circumferential surface of the valve body, passes through an opening portion of the valve body, then forms a spread flow in the fuel chamber. Thus, at the outflow side of the injection ports, it is possible to decrease collisions among fuel spray columns that are injected out of the injection ports.
However, by forming the fuel chamber between the valve seat and the injection ports, a dead volume in the fluid injection nozzle increases. When the dead volume is large, a relatively large amount of fuel is left in the fuel chamber without being injected out of the injection ports. For example, in a case that a fuel injection valve is installed in an intake pipe of an engine, the fuel left in the fuel chamber is sucked by intake air that flows through the intake pipe at a large speed. Thus, a fuel ratio in the intake air increases, and it becomes difficult to control the fuel injection amount with high accuracy.